This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Tomographic phase microscopy provides quantitative information and highly detailed structural information about a live cell. But in its current form, it can examine only a small number of cells at a time. To image large number of cells in short time, we have developed a new 3D phase microscopy, called as synthetic aperture tomography (SAT), which can be incorporated into the flow cytometry system. In SAT, a focused beam is illuminated onto a sample and the sample is scanned across the beam. After obtaining both phase and amplitude images of transmitted focused beam as a function of sample position, images are synthesized to generate a set of angular projection phase images. By applying filtered back-projection algorithm, we could map the 3D distribution of refractive index in live cells.